Add a BarrierClosure.

base/barrier_closure_unittest.cc

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/barrier_closure.h"
+
+#include "base/bind.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+void Increment(int* count) { (*count)++; }
+
+TEST(BarrierClosureTest, RunImmediatelyForZeroClosures) {
+  int count = 0;
+  base::Closure doneClosure(base::Bind(&Increment, base::Unretained(&count)));
+
+  base::Closure barrierClosure=base::BarrierClosure(0, doneClosure);

[awong, 2013/08/22 21:28:33]

spaces around = please.

[groby-ooo-7-16, 2013/08/22 21:59:45]

Done.

+  EXPECT_EQ(1, count);
+}
+
+TEST(BarrierClosureTest, RunAfterNumClosures) {
+  int count = 0;
+  base::Closure doneClosure(base::Bind(&Increment, base::Unretained(&count)));
+
+  base::Closure barrierClosure=base::BarrierClosure(2, doneClosure);

[awong, 2013/08/22 21:28:33]

spaces around = please.

[groby-ooo-7-16, 2013/08/22 21:59:45]

Done.

+  EXPECT_EQ(0, count);
+
+  barrierClosure.Run();
+  EXPECT_EQ(0, count);
+
+  barrierClosure.Run();
+  EXPECT_EQ(1, count);
+}